Various types of electrosurgical ground pads or dispersive electrodes have been devised to the end of affording a means of grounding the patient or dispersing current flow coming from the patient during an electrosurgical operation. Such ground pads have assumed different configurations according to the particular location of the body to which they are to be secured. Some of the first ground pads electrodes developed merely consisted of a flat metal plate having a connecting portion at one edge to facilitate interconnection of an electroconnector to the electrosurgical generator. It has also been proposed to employ thin metal plates or foil materials secured to a cardboard backing member. Other foil-type ground pads were devised in which a gel material was placed over the foil in order to effect a better electrical connection to the body while minimizing the risk of localized burning or hot spots often encountered with thin metal sheet or foil materials on account of their tendency to wrinkle.
Gels have become increasingly popular for use in connection with metal foil and are provided either separately or individually packaged so that the gel can be applied to the foil immediately prior to application of the pad to the body; or pre-gel ground pads electrodes are provided in which the pre-gel compound is encapsulated within an opening in the ground pad in direct electrical connection with the foil or other collector plate members. Generally, in the pre-gel types of ground pads electrodes, a connector may assume the form of a snap-type fastener electrically connected to the back of the collector plate to which may be affixed a lock-type of connector arrangement such as illustrated in U.S. Pat. No. 3,606,881 to Woodson; No. 3,895,635 to Justus, and No. 3,805,769 to Sessions.
The foregoing and other patents disclose the use of releasable connectors which can be attached to one end of the collector plate or to a tab projecting from one end of the plate. Generally, these connectors have demonstrated certain limitations either in failure to establish a positive connection, are subject to a certain amount of slippage or accidental loosening, or are limited in their freedom of movement once attached.
Electrodes which have been in most widespread use in electrosurgery are a conducting silver-silver chloride electrode which establishes a low impedance contact with the skin through a gel electrolyte. However, such conductive electrodes exhibit inadequacies which limit their effectiveness. For instance, the gels have a tendency to dry resulting in a significant increase in skin-to-electrode resistance which may produce unacceptably high current density levels. Bacterial and fungal growth can also take place in the gels, or a skin irritation often occurs when the electrolyte remains in contact with the skin for long periods of time. Wrinkling and flexing of these electrodes may increase the current density during an electrosurgical operation so that extreme tissue heating or RF burns may occur at the electrode site.
Accordingly, other so-called "dry" electrodes have been devised in addition to the more conventional metal plate or foil-type substrate, such as, for instance, the use of fine non-metallic electrically conductive particles which are applied directly by a solvent reactivated adhesive to the skin (Reinhold, Jr. U.S. Pat. No. 3,911,906 and Paine U.S. Pat. No. 3,547,105). The patent to Moe U.S. Pat. No. 3,566,860 discloses the use of a carbon-impregnated plastic in an adhesive coated web and also suggests utilization of a carbon or graphite with polytetrafluoroethylene while the patent to Woodson U.S. Pat. No. 3,606,881 is directed to the use of a pressure sensitive adhesive in combination with an electrode of silicon rubber with carbon, graphite or silver incorporated therein. U.S. Pat. No. 3,720,209 to Bolduc discloses a plate electrode of the type basically comprised of a one-piece flexible non-conductive sheet having a skin contacting electrically conductive layer with a clamp or jack-type electrical connector at one end. The patent to Maurer U.S. Pat. No. 3,817,252 teaches the use of conductive screens or foils in an EKG electrode.